It is known in the prior art to utilize rockshaft-mounted cams with provision for adjustment of the cams. One example is the control of a pair of side-by-side poppet valves in hydraulic mechanism, where rocking of the rockshaft and cams performs selective opening and closing of the valves. In such prior arrangement, the cam is adjustable only by relative rocking thereof with respect to the rocker element, so that such adjustment is confined to angular adjustment. Because the cam is relatively tightly journaled on the rockshaft, it cannot float during rocking. This requires precise machining of the cam faces to compensate for the relationship between the cam face and the follower on the poppet valve. Often, proper adjustment of the cam relative to one poppet valve adversely affects the relationship of the cam to the other valve. These disadvantages are eliminated, according to the present invention, by means enabling limited floating of the cam relative to the rockshaft and rocker element. This means involves a loose mounting of the cam on the rockshaft plus lost-motion means enabling the cam to move angularly with the rocker element about the rockshaft axis while permitting limited movement of the cam generally lengthwise of the rocker element. In a preferred embodiment, the lower end of the cam has an opening which loosely embraces the rockshaft so as to permit shifting of the cam relative to the rockshaft within the limits established by the excess of the diameter of the opening over that of the rockshaft. The lost-motion means includes a pin and slot connection spaced from the rockshaft which guides the cam back and forth in one direction radially of the rockshaft while enabling the cam to rock about the pin within the aforesaid limits. The adjustment means accomplishes adjustment of the cam relative to the rocker element within at least the aforesaid limits and within the futher limits established by the pin and slot connection.
Further features and advantages of the invention will become apparent to those versed in the art as a preferred embodiment of the invention is disclosed in detail in the following description and accompanying drawings .